Radar System Engineering

374 THE MAG.VETRON AA’D THE PULSER [SEC. 10.10
to 3 or 4 Mw by operating half a dozen high-voltage 6D21 thoriatedcathode
tetrodes in parallel. Figure 10.34 shows two views of a highpower
hard-tube pulser rated at 3 Mw and Fig. 10.35 shows a lightweight
hard-tube pulser built for airborne use. The latter is rated at 144 kw
output at pulse durations of 0.5, 1, and 2 psec; it employs a circuit very
similar to one given by combining Figs. 10.31 and 10.33.
1001O. Line-type Pulsers.—A schematic diagram applicable to most
typical line type pulsers is shown in Fig. 1036. Like the hard-tube
pulser, the line-type pulser is best analyzed by separate consideration of
Isolation or charging
impedance
Pulse forming network
---—— ----- -
I
Pulse transmission
cable
Despiking ‘
circuit
Damping
,----,
m!!?
i
1
,/ i ““--
I I
Load
m,
d= = :’a’
I
I
I
1,
●
* l__–_l +
FIa. 1036.-Basic circuit for a line-type pulser. Volta:c may be either d-c or some periodic
function of the timer SUC!I as V = V, sin 2~ft.
the discharging and the recharging circuit. The discharging circuit is
very simple, and its individual components are discussed in some detail
hereafter. The pulse transformer will be considered in the following section,
since it is applicable to both types of pulsers. In general, it can be
said that the effect of both the switch and the pulse transformer is to
decrease the rate of rise of voltage at the load from that which would be
produced by the network alone. The switch usually introduces an
appreciable resistance during its ionizing time, and the pulse transformer
introduces an additional inductance in series with the load. However, a
spike voltage is often encountered in practice, as mentioned previously,
because of the time required for the magnetron to draw current after
the normal voltage is applied to it. When it is necessary to prevent the
appearance of a spike, a “ despiking” circuit is used as indicated in the
diagram. The resistance of this circuit is chosen equal to the network